I am all for making things real for haunts. The more realistic the more terrifying. I would suggest using a real beat-up bat or wooden club. Yes, real. But the nails should be fake. At first I thought you could make the nails real too but only on one side giving patrons something to briefly touch and then the other side make the nails foam. This idea is way too dangerous and I advise using your best judgment. But, my actual answer here is to use a real bat and make foam nails.
How? pick up a can of Great Stuff Foam. Lay down some wax paper and and just spray out the foam in nail or pointed spike shapes. When they dry, paint them to resemble rusty nails. Then just glue them to the bat.
I hope this helps but be careful with this last idea, that great stuff foam breaks if you drop the bat.

Not to disagree here, but I would not go with sprayfoam for the nails, it is far to brittle. Use airline, the black airline that is about 1/8 of an inch ID. use a heatgun to get the bend out of it. You can drill through the bat and push the airline through the hole. then glue a roofing nail into the airline tube to make the head of the nail and trim the other end to a point. you can fill the line with caulk so it has a point. then paint the tube with chrome spraypaint then rust it up with brown and orange misted spray paint.
here is a pic of the airlineairline25.jpg